1. Field of the Invention
The present invention relates to a method for thermally decomposing either liquid or solid combustible material in a single reactor in the presence of working medium for generating and maintaining high active fluidization therefor. Further the present invention relates to an apparatus for carrying out the aforesaid method using the cylindrical reactor in which thermal decomposing and gasifying as well as burning and heating are performed with the aid of the circulating working medium heated at an elevated temperature.
2. Brief Description of the Prior Art
Hitherto known is a method in which two fluidized reactors are mounted with communication passages arranged therebetween, through which working medium in the form of powder-grain composite continuously circulates for the purpose of lightening heavy type crude oil by way of contact cracking so as to obtain kerosene or light oil. The inventor carried out a variety of research and development works for producing olefin by way of thermal decomposing in accordance with the aforesaid hitherto known method, resulting in four Japanese Pat. Nos. 606,666, 618,165, 625,300 and 768,886 granted. Further the inventor continued to carry out the aforesaid research and development works using the aforesaid known method for thermally decomposing solid combustible wastes by way of circulating sand as working medium, resulting in another two Japanese Pat. Nos. 871,982 and 911,193 granted.
It is pointed out as drawbacks with the above described prior methods, however, that the whole thermal decomposition system comprising the two fluidized reactors with the communicating means arranged for circulation therebetween is complicated in structure and not easy to be operated, that a large volume of thermal energy tends to be lost because of the wide surface of the whole assembly, particularly in case thermal decomposition reaction takes place at an elevated temperature, and that high thermal stress appears due to the complexity of the whole structure of the system.
In case of the conventional methods in which the working medium in the form of powder-grain composite circulate between the two fluidized reactors, gas is removed separately from the respective fluidized reactors. This ensures an advantage that high caloric combustible gas substantially free from nitrogen involved therein is produced even in case air is used for generating thermal energy for process operation in which either liquid or solid raw material is treated. For this reason it is recognized that the above described working medium circulation system is acceptable particularly for thermal decomposition of either liquid or solid combustible material such as pitch, asphalt, tar sand, bitumen, waste oil, heavy type crude oil, regular coal, brown coal, turf, peat, solid wastes inclusive combustible components therein from kitchen and factory, plant wastes from agriculture and forest industries, biomass manufactured for the purpose of generating thermal energy or the like, each of which is considered as useful energy source in near future.
It is to be noted, however, that among the above listed future energy sources waste oil, low caloric coal such as brown coal, turf and peat, miscellaneous wastes, industrial wastes, combustible wastes from agriculture and forest industries, biomass or the like is different from petroleum particularly in respect of operation scale, because a mass processing is not always acceptable for the former, whereas the latter is usually processed in a centralized installation in a large scale. It is rather economical for the former that a small or middle scale of installation is located therefor in position within or adjacent to the place where the former is collected or produced so that said installation serves as a local supply source of thermal energy.
As a typical case a wood working factory in an under-developed country will be exemplified. It is easy to collect wood wastes from forest industry as energy source. They are gasified to produce medium caloric combustible gas which is supplied to combustion engines or boilers. This results in saving in gasoline or oil.
It will be obvious that the aforesaid conventional methods in which the working medium in the form powder-grain composite circulates between the two fluidized reactors is preferable for generating thermal energy with the use of the aforesaid hitherto unused energy sources. But the prior methods are not always economically acceptable for a middle scale of operation, especially in case of a small scale of processing because of the complexity of the structure and operation of the whole system as well as the tendency of a large amount of heat loss therefrom.